In the typical manufacturing process for read/write heads for magnetic storage devices, a large number of sliders are fabricated from a single wafer having rows and columns of the magnetic transducers deposited simultaneously on a wafer surface using semiconductor-type process methods. In various process embodiments, further processing occurs after the wafer is sliced into rows or individual sliders. After slicing each slider has a magnetic head terminating the now exposed air-bearing surface (ABS). Additional processing typically forms the air-bearing features on the ABS.
In a recently described fabrication process, after the magnetic transducer structures have been formed, the wafer is sawed into individual sliders. The individual sliders are attached to an adhesive tape with the surface that will become the ABS (air-bearing surface) facing down. Use of robotic placement tools gives an array of sliders with defined spacing and rotational orientation. A frame or dam with thickness approximately equal to that of the slider is positioned around the outside edge of the array. A liquid such as an epoxy mixture is introduced into the corners and/or edges of the array and allowed to flow into all of the spaces surrounding the sliders. After curing, the sliders are partially encapsulated in the rigid matrix which protects the sides of the individual sliders in the array and provides both dimensional stability during bake and etch steps, as well, as solvent resistance during cleaning and stripping steps. The encapsulated slider array is repositioned so that the air-bearing surface is facing upwards. The array is attached to a fresh carrier by means of an adhesive. The tape over the ABS side is then removed. The slider array surface is planarizied to facilitate processing. An air-bearing pattern is etched into the slider surface using standard photolithography, RIE etch process methodology, etc. Finally the slider array is detached from the carrier and the encapsulation material removed by solvent.
The matrix material between the sliders in the array must withstand a number of stresses including: RIE etch exposure, UV light, temperature cycling up to 110 C, and exposure to several liquids including photoresist solutions, base-containing photoresist developers, propylene glycol methyl ether acetate, IPA, NMP, and water. The encapsulant material must withstand all these conditions without being softened, removed, or distorted by solvent uptake. Damage or distortion of the encapsulant material will result in slider registration failure (resulting in poor lithographic patterning), or photoresist coating flaws; both of which drastically reduce the product yield. After all the fabrication processes are complete, the sliders must be freed from the encapsulant matrix without any matrix material contamination of the slider surfaces. While the resistance to the processing solvents is a requirement, this resistance also makes removing the epoxy difficult.
Outside of the slider processing field release coating compositions have been used for application to various substrates, whereby various materials may be placed in adhering contact with such release-coated substrates and may be easily released at a subsequent time. Release coating compositions commonly in use in commercial and industrial processes contain conventional release agents, such as a silicone polymer, or a stearate chromium complex, or other relatively expensive materials, or other relatively less expensive release agents, such as polyvinyl alcohol.
The invention described in U.S. Pat. No. 5,077,175 to Fryd, et al. concerns a plasticized polyvinyl alcohol release composition for an aqueous or semi-aqueous processible flexographic printing plate comprising: (a) at least 60% of a substantially hydrolyzed polyvinyl alcohol based on the total weight of the release composition; and (b) at least 8% plasticizer, based on the total weight of the release composition.
U.S. Pat. No. 4,440,830 to Wempe describes the use of a polyvinyl alcohol based release coating compositions for strippable substrates which are in contact with pressure sensitive adhesives. Substrates coated with the release compositions are easily peeled from pressure sensitive adhesive coated substrates without substantially adversely affecting the adhesive character of the adhesive coated substrate. The release coating composition comprises polyvinyl alcohol, a migratable release promoting agent, a water soluble salt of a coordinating metal and a water soluble boron compound in an aqueous solution. In addition to composites comprising release coated substrates affixed to adhesive coated substrates, the release compositions can be applied to the backing of a pressure sensitive adhesive tape to permit facile uncoiling of the rolled tape product.
The prior art does not provide a teaching of a method of processing sliders wherein a suitable encapsulation material can be cleanly removed from the sliders at the proper time during the process.